Method for patterning a low activation energy photoresist

ABSTRACT

Polymers containing an acetal or ketal linkage and their use in lithographic photoresist compositions, particularly in chemical amplification photoresists, are provided. The polymer is prepared from at least one first olefinic monomer containing an acetal or ketal linkage, the acid-catalyzed cleavage of which renders the polymer soluble in aqueous base; and at least one second olefinic monomer selected from (i) an olefinic monomer containing a pendant fluorinated hydroxyalkyl group R H , (ii) an olefinic monomer containing a pendant fluorinated alkylsulfonamide group R S , and (iii) combinations thereof. The acetal or ketal linkage may be contained within an acid-cleavable substituent R CL  in the first olefinic monomer. A method for using the photoresist compositions containing these polymers in preparing a patterned substrate is also provided in which the polymer is rendered soluble in aqueous base at a temperature of less than about 100° C. by acid-catalyzed deprotection of pendent acetal- or ketal-protected carboxylic acid groups.

TECHNICAL FIELD

This invention relates generally to the field of photolithography. Morespecifically, the invention relates to polymers containing an acetal orketal linkage and their use in lithographic photoresist compositions,particularly in chemical amplification photoresists.

BACKGROUND OF THE INVENTION

The patterning of radiation sensitive polymeric films with high energyradiation such as photons, electrons, or ion beams is the principlemeans of defining high resolution circuitry found in semiconductordevices. The radiation sensitive films, often referred to asphotoresists regardless of the radiation source, generally consist ofmulticomponent formulations that are coated onto a desired substratesuch as a silicon wafer. The radiation is most commonly ultravioletlight at wavelengths of 436, 365, 257, 248, 193 or 157 nanometers (nm),or a beam of electrons or ions, or ‘soft’ x-ray radiation, also referredto as extreme ultraviolet (EUV) or x-rays. The radiation is exposedpatternwise and induces a chemical transformation that renders thesolubility of the exposed regions of the films different from that ofthe unexposed areas when the films are treated with an appropriatedeveloper, usually a dilute, basic aqueous solution, such as aqueoustetramethylammonium hydroxide (TMAH).

Typical photoresists contain a polymeric component and are generallycomprised of a polymeric matrix, a radiation sensitive component, acasting solvent, and other performance enhancing additives. The highestperforming photoresists in terms of sensitivity to radiation andresolution capability are “chemically-amplified” photoresists, allowinghigh resolution, high contrast and high sensitivity that are notgenerally provided by other photoresists. Chemically amplifiedphotoresists are based on a catalytic mechanism that allows a relativelylarge number of chemical events such as, for example, deprotectionreactions in the case of positive photoresists or crosslinking reactionsin the case of negative tone photoresists, to be brought about by theapplication of a relatively low dose of radiation that induces formationof the catalyst, often a strong acid.

Although chemically-amplified resists have been developed for 248, 193and 157 nm lithography, certain barriers to achieving higher resolutionand smaller feature sizes remain due to physical, processing andmaterial limitations. One such phenomenon that arises for imaging in thesub-50 nm regime, resulting in diminished image integrity in thepattern, is referred to as “image blur” (see, e.g., Hinsberg et al.,Proc. SPIE, (2000), 3999, 148 and Houle et al., J. Vac. Sci. Technol B,(2000), 18, 1874). Image blur is generally thought to result from twocontributing factors: gradient-driven acid diffusion and reactionpropagation, the result being a distortion in the developable imagecompared to the projected aerial image transferred onto the film.Although, both factors contribute to image blur, the degree of theeffect from each is different. Temperature also has a differing effecton each factor.

Acid diffusion is further thought to depend on several factors,including the type of photoacid generator (PAG) and the mobility in thephotoresist polymer. In turn, the acid mobility in the polymer isdependent on a variety of factors, including, among others, the chemicalfunctionality of the polymer, and the temperature and time of bakingduring resist processing.

Reaction propagation likewise depends on a number of factors, such asthe activation energy (enthalpy) and the volatility of products(entropy).

Thus, as the need for better resolutions, minimum feature sizes,improved sensitivity and process latitude increases, image blur due toboth contributing factors must be mininized. While both may be reducedto a degree by the use of acid-quenchers, or bases, the extent ofthermally induced image blur estimated to be on the order of 10-50 nmwith conventional resists and processing (see also Breyta et al., U.S.Pat. No. 6,227,546) suggests that improvements are necessary in order toachieve sub-50 nm imaging.

An ongoing need therefore exists for new photoresist materials andcompositions, as well as methods of patterning substrates, which canlead to improved high resolution photoresist applications.

SUMMARY OF THE INVENTION

The present invention addresses the aforementioned needs in the art, andprovides improved polymers and photoresist compositions that areparticularly suitable for photolithographic applications.

In one aspect of the invention, polymers containing an acetal or ketallinkage are provided that are suitable for incorporation intolithographic photoresist compositions. The polymer is prepared from atleast one first olefinic monomer containing an acetal or ketal linkage,the acid-catalyzed cleavage of which renders the polymer soluble inaqueous base; and at least one second olefinic monomer selected from (i)an olefinic monomer containing a pendant fluorinated hydroxyalkyl groupR^(H), (ii) an olefinic monomer containing a pendant fluorinatedalkylsulfonamide group R^(S), and (iii) combinations thereof. The acetalor ketal linkage may be contained within an acid-cleavable substituentR^(CL) in the first olefinic monomer. The acid cleavable substituentR^(CL) is preferably a relatively reactive group, such that the processof cleaving R^(CL) from the polymer has a fairly low activation energy.In this way, following exposure of the polymer to acid, e.g., aphotogenerated acid, R^(CL) can be cleaved from the polymer at atemperature that is sufficiently low to minimize certain disadvantageousconditions, such as image blur, by limiting the extent of acid diffusionand reaction propagation. Comonomers containing additionalacid-cleavable substituents R^(CL*), acid-inert polar groups R^(P),and/or acid-inert nonpolar groups R^(NP) may also be copolymerized withthe first and second olefinic monomers to further modify the propertiesof the inventive polymer.

In another aspect of the invention, photoresist compositions areprovided containing a photoacid generator in addition to the inventivepolymer. These compositions may additionally contain other components,e.g., an additive such as a dissolution-modifying additive.

In a further aspect of the invention, a method for using the photoresistcompositions containing these polymers in preparing a patternedsubstrate is also provided in which the polymer is rendered soluble inaqueous base at a temperature of less than about 100° C. byacid-catalyzed deprotection of pendent acetal- or ketal-protectedcarboxylic acid groups. In this regard, the photoresist compositions areuseful in a process for patterning a substrate by:

-   -   (a) coating the substrate with a film of a photoresist        composition comprised of (i) a polymer that is rendered soluble        in aqueous base at a temperature of less than about 100° C. by        acid-catalyzed deprotection of pendent acetal- or        ketal-protected carboxylic acid groups, and (ii) a photoacid        generator; (b) patternwise exposing the film to an imaging        radiation source so as to form a latent, patterned image in the        film; (c) baking the exposed film at a post-exposure bake        temperature below about 100° C.; and (d) developing the latent        image with a developer to form a patterned substrate. The        developer is selected so as to render the exposed regions of the        film soluble. The surface of the substrate which is coated with        the photoresist may be a semiconductor, ceramic, metallic, or        organic material (e.g., an organic dielectric material or an        organic underlayer of a bilayer resist). Exposure may be carried        out using electron-beam, x-ray, or ultraviolet radiation,        although radiation in the DUV and EUV, including 193 nm, 157 nm,        and 13.4 nm, is preferred.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B depict contrast curves for a fluoroacrylate resistmaterial (Ex-FARM) based upon a copolymer of NBHFAMA(3-(5-Bicyclo-[2,2,1]hept-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)-2-propanolmethacrylate) and ALMA (alpha-angelicalactone methacrylate).

FIG. 2 depicts SEM photomicrographs of a NBHFAMA/ALMA copolymer resistapplied to a chrome-on-glass (COG) substrate and exposed at 193 nm.

FIG. 3 depicts contrast curves for a resist material based upon acopolymer of THFMA (2-tetrahydrofuranyl methacrylate) and NBHFA(3-(5-Bicyclo-[2,2,1]heptene-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)-2-propanol)for various post exposure bake (PEB) temperatures.

FIG. 4 depicts an SEM photomicrograph of a THFMA/NBHFA copolymer resistprepared at a post exposure bake (PEB) temperature of 50° C. and a doseof 50.4 mJ/cm2.

FIG. 5 depicts contrast curves for a resist material based upon acopolymer of THPMA (2-tetrahydropyranyl methacrylate) and NBHFAMA(3-(5-Bicyclo-[2,2,1]hept-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)-2-propanolmethacrylate) for various post exposure bake (PEB) temperatures.

FIG. 6 depicts an SEM photomicrograph of the resist of FIG. 5 for a PEBof 80° C. and a dose of 31 mJ/cm2.

DETAILED DESCRIPTION OF THE INVENTION

I. Definitions and Nomenclature

Unless otherwise indicated, this invention is not limited to specificcompositions, components, or process steps. It should also be noted thatthe singular forms “a” and “the” are intended to encompass pluralreferents, unless the context clearly dictates otherwise. Theterminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting.

In this specification and in the claims that follow, reference will bemade to a number of terms, which shall be defined to have the followingmeanings:

As used herein, the phrase “having the formula” or “having thestructure” is not intended to be limiting and is used in the same waythat the term “comprising” is commonly used.

The term “alkyl” as used herein refers to a linear or branched,saturated hydrocarbon substituent that generally, although notnecessarily, contains 1 to about 24 carbon atoms, such as methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, octyl, decyl,tetradecyl, hexadecyl, eicosyl, tetracosyl, and the like. Generally,although again not necessarily, alkyl groups herein contain 1 to about12 carbon atoms. The term “lower alkyl” intends an alkyl group of 1 to 6carbon atoms, and the term “cycloalkyl” intends a cyclic alkyl group,typically having 3 to 12, preferably 3 to 8, carbon atoms. The term“substituted alkyl” refers to alkyl substituted with one or moresubstituent groups, i.e., wherein a hydrogen atom is replaced with anon-hydrogen substituent group, and the terms “heteroatom-containingalkyl” and “heteroalkyl” refer to alkyl substituents in which at leastone carbon atom is replaced with a heteroatom such as O, N, or S. If nototherwise indicated, the terms “alkyl” and “lower alkyl” include linear,branched, cyclic, unsubstituted, substituted, and/orheteroatom-containing alkyl and lower alkyl, respectively.

The term “alkylene” as used herein refers to a difunctional linear orbranched saturated hydrocarbon linkage, typically although notnecessarily containing 1 to about 24 carbon atoms, such as methylene,ethylene, n-propylene, n-butylene, n-hexylene, decylene, tetradecylene,hexadecylene, and the like. Preferred alkylene linkages contain 1 toabout 12 carbon atoms, and the term “lower alkylene” refers to analkylene linkage of 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms.The term “substituted alkylene” refers to an alkylene linkagesubstituted with one or more substituent groups, i.e., wherein ahydrogen atom is replaced with a non-hydrogen substituent group, and theterms “heteroatom-containing alkylene” and “heteroalkylene” refer toalkylene linkages in which at least one carbon atom is replaced with aheteroatom. If not otherwise indicated, the terms “alkylene” and “loweralkylene” include linear, branched, cyclic, unsubstituted, substituted,and/or heteroatom-containing alkylene and lower alkylene, respectively.

The term “alkoxy” as used herein refers to a group —O-alkyl wherein“alkyl” is as defined above.

The term “alicyclic” is used to refer to cyclic, non-aromatic compounds,substituents and linkages, e.g., cycloalkanes and cycloalkenes,cycloalkyl and cycloalkenyl substituents, and cycloalkylene andcycloalkenylene linkages. Often, the term refers to polycycliccompounds, substituents, and linkages, including bridged bicyclic,compounds, substituents, and linkages. Preferred alicyclic moietiesherein contain 3 to about 30, typically 5 to about 14, carbon atoms.Unless otherwise indicated, the term “alicyclic” includes substitutedand/or heteroatom-containing such moieties. It will be appreciated thatthe term “cyclic,” as used herein, thus includes “alicyclic” moieties.

The term “heteroatom-containing” as in a “heteroatom-containing alkylgroup” (also termed a “heteroalkyl” group) refers to a molecule, linkageor substituent in which one or more carbon atoms are replaced with anatom other than carbon, e.g., nitrogen, oxygen, sulfur, phosphorus orsilicon, typically nitrogen, oxygen or sulfur. Similarly, the term“heteroalkyl” refers to an alkyl substituent that isheteroatom-containing, the term “heterocyclic” refers to a cyclicsubstituent that is heteroatom-containing. Examples of heteroalkylgroups include alkoxyalkyl, alkylsulfanyl-substituted alkyl, and thelike.

Unless otherwise indicated, the term “hydrocarbyl” is to be interpretedas including substituted and/or heteroatom-containing hydrocarbylmoieties. “Hydrocarbyl” refers to univalent hydrocarbyl radicalscontaining 1 to about 30 carbon atoms, preferably 1 to about 18 carbonatoms, most preferably 1 to about 12 carbon atoms, including linear,branched, cyclic, alicyclic, and aromatic species. “Substitutedhydrocarbyl” refers to hydrocarbyl substituted with one or moresubstituent groups, and the terms “heteroatom-containing hydrocarbyl”and “heterohydrocarbyl” refer to hydrocarbyl in which at least onecarbon atom is replaced with a heteroatom.

By “substituted” as in “substituted alkyl,” and the like, as alluded toin some of the aforementioned definitions, is meant that in the alkyl,or other moiety, at least one hydrogen atom bound to a carbon (or other)atom is replaced with a non-hydrogen substituent. Examples of suitablesubstituents herein include halo, hydroxyl, sulfhydryl, C₁-C₁₂ alkoxy,acyl (including C₂-C₁₂ alkylcarbonyl (—CO-alkyl)), acyloxy (—O-acyl),C₂-C₁₂ alkoxycarbonyl (—(CO)—O-alkyl), C₂-C₁₂ alkylcarbonato(—O—(CO)—O-alkyl), carboxy (—COOH), carbamoyl (—(CO)—NH₂),mono-substituted C₁-C₁₂ alkylcarbamoyl (—(CO)—NH(C₁-C₁₂ alkyl)),di-substituted alkylcarbamoyl (—(CO)—N(C₁-C₁₂ alkyl)₂), cyano (—C≡N),cyanato (—O—C≡N), formyl (—(CO)—H), amino (—NH₂), mono- and di-(C₁-C₁₂alkyl)-substituted amino, mono- and C₂-C₁₂ alkylamido (—NH—(CO)-alkyl),imino (—CR═NH where R=hydrogen, C₁-C₁₂ alkyl. etc.), alkylimino(—CR═N(alkyl), where R=hydrogen, alkyl, etc.), C₁-C₂₀ alkylsulfanyl(—S-alkyl; also termed “alkylthio”), C₅-C₁₈ arylsulfanyl (—S-aryl; alsotermed “arylthio”), C₁-C₂₀ alkylsulfinyl (—(SO)-alkyl), C₁-C₂₀alkylsulfonyl (SO₂-alkyl), phosphono (—P(O)(OH)₂), and the hydrocarbylmoieties C₁-C₂₄ alkyl (preferably C₁-C₁₂ alkyl). In addition, theaforementioned functional groups may, if a particular group permits, befurther substituted with one or more additional functional groups orwith one or more hydrocarbyl moieties such as those specificallyenumerated above. Analogously, the above-mentioned hydrocarbyl moietiesmay be further substituted with one or more functional groups oradditional hydrocarbyl moieties such as those specifically enumerated.When the term “substituted” appears prior to a list of possiblesubstituted groups, it is intended that the term apply to every memberof that group.

The term “fluorinated” refers to replacement of a hydrogen atom in amolecule or molecular segment with a fluorine atom, and includesperfluorinated moieties. The term “perfluorinated” is also used in itsconventional sense to refer to a molecule or molecular segment whereinall hydrogen atoms are replaced with fluorine atoms. Thus, a“fluorinated” methyl group encompasses —CH₂F and —CHF₂ as well as the“perfluorinated” methyl group, i.e., —CF₃ (trifluoromethyl). The term“fluoroalkyl” refers to a fluorinated alkyl group, the term“fluoroalkylene” refers to a fluorinated alkylene linkage, the term“fluoroalicyclic” refers to a fluorinated alicyclic moiety, and thelike.

“Optional” or “optionally” means that the subsequently describedcircumstance may or may not occur, so that the description includesinstances where the circumstance occurs and instances where it does not.For example, the phrase “optionally substituted” means that anon-hydrogen substituent may or may not be present on a given atom, and,thus, the description includes structures wherein a non-hydrogensubstituent is present and structures wherein a non-hydrogen substituentis not present.

The term “acid-cleavable” refers to a molecular segment containing atleast one covalent bond that is cleaved upon exposure to acid.Typically, the reaction of acid-cleavable groups herein withphotogenerated acid occurs only, or is promoted greatly by, theapplication of heat. Those skilled in the art will recognize the variousfactors that influence the rate and ultimate degree of cleavage ofacid-cleavable groups as well as the issues surrounding integration ofthe cleavage step into a viable manufacturing process. The product ofthe cleavage reaction is generally an acidic group, which, when presentin sufficient quantities, imparts solubility to the polymers of theinvention in basic aqueous solutions.

Analogously, the term “acid-inert” refers to a substituent that is notcleaved or otherwise chemically modified upon contact withphotogenerated acid.

The terms “photogenerated acid” and “photoacid” are used interchangeablyherein to refer to the acid that is created upon exposure of the presentphotoresist compositions to radiation, by virtue of the photoacidgenerator contained in the compositions.

The term “substantially transparent” as used to describe a polymer thatis “substantially transparent” to radiation of a particular wavelengthrefers to a polymer that has an absorbance of less than about5.0/micron, preferably less than about 3.0/micron, most preferably lessthan about 1.5/micron, at a selected wavelength.

For additional information concerning terms used in the field oflithography and lithographic compositions, see Introduction toMicrolithography, Eds. Thompson et al. Washington, D.C.: AmericanChemical Society, 1994).

II. Novel Polymers

In general, the polymers of the invention are formed from at least onefirst olefinic monomer containing an acetal or ketal linkage, theacid-catalyzed cleavage of which renders the polymer soluble in aqueousbase; and at least one second olefinic monomer selected from (i) anolefinic monomer containing a pendant fluorinated hydroxyalkyl groupR^(H), (ii) an olefinic monomer containing a pendant fluorinatedalkylsulfonamide group R^(S), and (iii) combinations thereof.

The acetal or ketal linkage generally, although not necessarily, may becontained within acid-cleavable substituent R^(CL) in the first olefinicmonomer, the acid-cleavable substituent having the structure-(L¹)_(m)—(X)_(n)-(L²)_(q)—R¹  (I)

-   -   in which m, n, and q are independently zero or 1;    -   L¹ is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂        alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂        heteroalkylene, and further wherein when L¹ is optionally        substituted and/or heteroatom-containing C₁-C₁₂ alkylene, L¹ may        be linear, branched, or cyclic;    -   X is selected from C₃-C₃₀ alicyclic and substituted C₃-C₃₀        alicyclic;    -   L² is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂        alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂        heteroalkylene, and further wherein when L² is optionally        substituted and/or heteroatom-containing C₃-C₁₂ alkylene, L may        be linear, branched, or cyclic; and    -   R¹ is selected from acetal-containing and ketal-containing        substituents.

In preferred R^(CL) substituents:

-   -   L¹ is selected from C₁-C₁₂ alkylene, particularly C₁-C₆        alkylene, and heteroatom-containing C₁-C₁₂ alkylene;    -   X is C₃-C₁₈ alicyclic, particularly C₆-C₁₂ alicyclic;    -   L² is selected from C₁-C₁₂ alkylene, hydroxyl-substituted C₁-C₁₂        alkylene, C₁-C₁₂ fluoroalkylene, and hydroxyl-substituted C₁-C₁₂        fluoroalkylene; and    -   R¹ has the structure —(CO)—O—CR⁴R⁵—O—CR⁶R⁷R⁸ in which R⁴, R⁵,        R⁶, R⁷, and R⁸ are selected so as to render R¹ acid-cleavable.

Preferably, L² is of the formula —CR⁹R¹⁰—wherein R⁹ is hydrogen, C₁-C₁₂alkyl, or C₁-C₁₂ fluoroalkyl, and R¹⁰ is C₁-C₁₂ alkyl or C₁-C₁₂fluoroalkyl; and R⁴, R⁵, R⁶, R⁷, and R⁸ are independently selected fromhydrogen, C₄-C₁₂ hydrocarbyl, substituted C₄-C₁₂ hydrocarbyl,heteroatom-containing C₄-C₁₂ hydrocarbyl, and substitutedheteroatom-containing C₄-C₁₂ hydrocarbyl, and further wherein any two ofR⁴, R⁵, R⁶, R⁷, and R⁸ may be linked to form a cyclic group.

In the case where the second olefinic monomer contains a pendantfluorinated hydroxyalkyl group R^(H), it is preferred that RH has thestructure -L³-CR¹¹R¹²—OH, in which:

-   -   L³ is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂        alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂        heteroalkylene, C₃-C₁₅ alicyclic, C₃-C₁₅ fluoroalicyclic, and        combinations thereof;    -   R¹¹ is selected from hydrogen, C₁-C₂₄ alkyl, and substituted        C₁-C₂₄ alkyl; and    -   R¹² is C₁-C₂₄ alkyl or fluorinated C₁-C₂₄ alkyl, with the        proviso that at least one of R¹¹ and R¹² is fluorinated; and        further wherein R¹¹ and R¹² can be taken together to form a        ring.

In addition, R¹¹ may be selected from hydrogen, C₁-C₁₂ alkyl, and C₁-C₁₂haloalkyl, and R¹² is C₁-C₁₂ alkyl or fluorinated C₁-C₁₂ alkyl;preferably, R¹¹ is selected from hydrogen, C₁-C₈ alkyl, and fluorinatedC₁-C₈ alkyl, and R¹² is C₁-C₈ alkyl or fluorinated C₁-C₈ alkyl; and morepreferably, R¹¹ is selected from hydrogen, C₁-C₄ alkyl, semi-fluorinatedC₁-C₄ alkyl, and perfluorinated C₁-C₄ alkyl, and R¹² is C₁-C₄ alkyl,semi-fluorinated C₁-C₄ alkyl, or perfluorinated C₁-C₄ alkyl. It is mostpreferred that R¹¹ and R¹² are both trifluoromethyl.

In the case where the second olefinic monomer contains a pendantfluorinated alkylsulfonamide group R^(S), it is preferred that R^(S) hasthe structure -L³-SO₂—NHR¹⁶, in which:

-   -   L³ is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂        alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂        heteroalkylene, C₃-C₁₅ alicyclic, C₃-C₁₅ fluoroalicyclic,        combinations thereof; and    -   R¹⁶ is selected from C₁-C₂₄ alkyl and substituted C₁-C₂₄ alkyl,        C₁-C₂₄ fluoroalkyl and substituted C₁-C₂₄ fluoroalkyl.

In another aspect, the polymer may be formed from a first olefinicmonomer unit having the structure of formula (II)

-   -   and a second olefinic monomer unit having the structure of        formula (III)        wherein m, n, and q are independently zero or 1;    -   L¹ is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂        alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂        heteroalkylene, and further wherein when L¹ is optionally        substituted and/or heteroatom-containing C₁-C₁₂ alkylene, L¹ may        be linear, branched, or cyclic;    -   X is selected from C₃-C₃₀ alicyclic and substituted C₃-C₃₀        alicyclic;    -   L² is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂        alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂        heteroalkylene, and further wherein when L² is optionally        substituted and/or heteroatom-containing C₃-C₁₂ alkylene, L may        be linear, branched, or cyclic; and    -   R¹ is selected from acetal-containing and ketal-containing        substituents;    -   L³ is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂        alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂        heteroalkylene, C₃-C₁₅ alicyclic, C₃-C₁₅ fluoroalicyclic, and        combinations thereof;    -   R₁₁ is selected from hydrogen, C₁-C₂₄ alkyl, and substituted        C₁-C₂₄ alkyl;    -   R¹² is C₁-C₂₄ alkyl or fluorinated C₁-C₂₄ alkyl, with the        proviso that at least one of R¹¹ and R¹² is fluorinated; and        further wherein R¹¹ and R¹² can be taken together to form a        ring.    -   R¹³ and R^(13A) are independently selected from hydrogen,        fluorine, C₁-C₂₄ alkyl, substituted C₁-C₂₄ alkyl, C₁-C₂₄ alkoxy,        and substituted C₁-C₂₄ alkoxy; and    -   R¹⁴ and R^(14A) are independently selected from hydrogen,        fluorine, C₁-C₂₄ alkyl and substituted C₁-C₂₄ alkyl; and

R¹⁵ and R^(15A) are independently selected from hydrogen, fluorine,C₁-C₂₄ alkyl, and substituted C₁-C₂₄ alkyl, and further wherein any twoof L¹, R¹³, R⁴, and R¹⁵ may be taken together to form a ring and any twoof L³, R^(13A), R^(14A), and R^(15A) may be taken together to form aring.

Preferred substituents for polymers having units of formulae (II) and(III) include:

-   -   L¹ is selected from C₁-C₁₂ alkylene, particularly C₁-C₆        alkylene, and heteroatom-containing C₁-C₁₂ alkylene;    -   X is C₃-C₁₈ alicyclic, particularly C₆-C₁₂ alicyclic;    -   L² is selected from C₁-C₁₂ alkylene, hydroxyl-substituted C₁-C₁₂        alkylene, C₁-C₁₂ fluoroalkylene, and hydroxyl-substituted C₁-C₁₂        fluoroalkylene;    -   R¹ has the structure —(CO)—O—CR⁴R⁵—O—CR⁶R⁷R⁸ in which R⁴, R⁵,        R⁶, R⁷, and R⁸ are selected so as to render R¹ acid-cleavable;    -   R¹¹ is selected from hydrogen, C₁-C₁₂ alkyl, and C₁-C₁₂        haloalkyl; and    -   R¹¹ is C₁-C₁₂ alkyl or fluorinated C₁-C₁₂ alkyl; and further        wherein R¹¹ and R¹² can be taken together to form a ring.

As noted above, preferably, L² is of the formula —CR⁹R¹⁰—, wherein R⁹ ishydrogen, C₁-C₁₂ alkyl, or C₁-C₁₂ fluoroalkyl, and R¹⁰ is C₁-C₁₂ alkylor C₁-C₁₂ fluoroalkyl; and R⁴, R⁵, R⁶, R⁷, and R⁸ are independentlyselected from hydrogen, C₄-C₁₂ hydrocarbyl, substituted C₄-C₁₂hydrocarbyl, heteroatom-containing C₄-C₁₂ hydrocarbyl, and substitutedheteroatom-containing C₄-C₁₂ hydrocarbyl, and further wherein any two ofR⁴, R⁵, R⁶, R⁷, and R⁸ may be linked to form a cyclic group. Also, inadditional aspects, R¹¹ may be selected from hydrogen, C₁-C₁₂ alkyl, andC₁-C₁₂ haloalkyl, and R¹² is C₁-C₁₂ alkyl or fluorinated C₁-C₁₂ alkyl;preferably, R¹¹ is selected from hydrogen, C₁-C₈ alkyl, and fluorinatedC₁-C₈ alkyl, and R¹² is C₁-C₈ alkyl or fluorinated C₁-C₈ alkyl; and morepreferably, R¹ is selected from hydrogen, C₁-C₄ alkyl, semi-fluorinatedC₁-C₄ alkyl, and perfluorinated C₁-C₄ alkyl, and R¹² is C₁-C₄ alkyl,semi-fluorinated C₁-C₄ alkyl, or perfluorinated C₁-C₄ alkyl. It is mostpreferred that R¹¹ and R¹² are both trifluoromethyl.

The polymer may also be formed from a first olefinic monomer unit havingthe structure of formula (II)

and a second olefinic monomer unit having the structure of formula (IV)

-   -   wherein m, n, and q are independently zero or 1;    -   L¹ is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂        alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂        heteroalkylene, and further wherein when L¹ is optionally        substituted and/or heteroatom-containing C₁-C₁₂ alkylene, L¹ may        be linear, branched, or cyclic;    -   X is selected from C₃-C₃₀ alicyclic and substituted C₃-C₃₀        alicyclic;    -   L² is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂        alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂        heteroalkylene, and further wherein when L² is optionally        substituted and/or heteroatom-containing C₃-C₁₂ alkylene, L² may        be linear, branched, or cyclic; and    -   R¹ is selected from acetal-containing and ketal-containing        substituents;    -   L³ is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂        alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂        heteroalkylene, C₃-C₁₅ alicyclic, C₃-C₁₅ fluoroalicyclic, and        combinations thereof;    -   R¹³ and R^(13A) are independently selected from hydrogen,        fluorine, C₁-C₂₄ alkyl, substituted C₁-C₂₄ alkyl, C₁-C₂₄ alkoxy,        and substituted C₁-C₂₄ alkoxy; and

R¹⁴ and R^(14A) are independently selected from hydrogen, fluorine,C₁-C₂₄ alkyl and substituted C₁-C₂₄ alkyl;

-   -   R¹⁵ and R^(15A) are independently selected from hydrogen,        fluorine, C₁-C₂₄ alkyl, and substituted C₁-C₂₄ alkyl, and        further wherein any two of L₁, R¹³, R¹⁴, and R¹⁵ may be taken        together to form a ring and any two of L³, R^(13A), R^(14A), and        R^(15A) may be taken together to form a ring; and    -   R¹⁶ is selected from C₁-C₂₄ alkyl and substituted C₁-C₂₄ alkyl,        C₁-C₂₄ fluoroalkyl and substituted C₁-C₂₄ fluoroalkyl.

Preferred substituents for polymers having units of formulae (II) and(IV) include:

-   -   L¹ is selected from C₁-C₁₂ alkylene, particularly C₁-C₆        alkylene, and heteroatom-containing C₁-C₁₂ alkylene;    -   X is C₃-C₁₈ alicyclic, particularly C₆-C₁₂ alicyclic;    -   L² is selected from C₁-C₁₂ alkylene, hydroxyl-substituted C₁-C₁₂        alkylene, C₁-C₁₂ fluoroalkylene, and hydroxyl-substituted C₁-C₁₂        fluoroalkylene; and    -   R¹ has the structure —(CO)—O—CR⁴R⁵—O—CR⁶R⁷R⁸ in which R⁴, R⁵,        R⁶, R⁷, and R⁸ are selected so as to render R¹ acid-cleavable.

As noted above, preferably, L² is of the formula —CR⁹R¹⁰—, wherein R⁹ ishydrogen, C₁-C₁₂ alkyl, or C₁-C₁₂ fluoroalkyl, and R¹⁰ is C₁-C₁₂ alkylor C₁-C₁₂ fluoroalkyl; and R⁴, R⁵, R⁶, R⁷, and R⁸ are independentlyselected from hydrogen, C₄-C₁₂ hydrocarbyl, substituted C₄-C₁₂hydrocarbyl, heteroatom-containing C₄-C₁₂ hydrocarbyl, and substitutedheteroatom-containing C₄-C₁₂ hydrocarbyl, and further wherein any two ofR⁴, R⁵, R⁶, R⁷, and R⁸ may be linked to form a cyclic group.

Preferred representative monomers suitable for forming the polymermonomer units of formula (II) include, without limitation:

-   -   where R is selected from hydrogen, fluorine, C₁-C₂₄ alkyl, and        fluorinated C₁-C₂₄ alkyl.

The polymer may also be formed from a mixture of two or more differentfirst monomers and may also include at least one additional olefiniccomonomer, e.g., thereby forming ter-, tetra- or multi-monomer polymers.While not strictly limited, such additional monomers include monomerscontaining an acid-cleavable substituent R^(CL*); monomers containing anacid-inert, polar substituent, R^(P); monomers containing an acid-inert,nonpolar substituent, R^(NP); and combinations thereof.

The additional monomers containing an acid-cleavable substituent R^(CL*)are not limited to particular groups, and may include acid-cleavableester, oligomeric ester, ether, carbonate, orthoester substituents, andthe like. Such groups provide additional flexibility by allowing for theacid activation to be tailored as desired, e.g., by combining a lowactivation energy acid-cleavable group with a higher activation energyacid-cleavable group. Generally, although not necessarily, the acetal orketal linkage may be contained within an acid-cleavable substituentR^(CL*) in the additional olefinic monomer, the acid-cleavablesubstituent having the structure-(L^(1*))_(m*)—(X*)_(n*)—[(L^(2*))_(q*)—R^(1*)]_(r*)  (V)

-   -   in which m*, n*, and q* are independently zero or 1;    -   r* is an integer of at least 1;    -   L^(1*) is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂        alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂        heteroalkylene, and further wherein when L^(1*) is optionally        substituted and/or heteroatom-containing C₃-C₁₂ alkylene, L^(1*)        may be linear, branched, or cyclic;    -   X* is selected from C₃-C₃₀ alicyclic and substituted C₃-C₃₀        alicyclic;    -   L^(2*) is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂        alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂        heteroalkylene, and further wherein when L^(2*) is optionally        substituted and/or heteroatom-containing C₃-C₁₂ alkylene, L^(2*)        may be linear, branched, or cyclic; and    -   R^(1*) is selected from acid-cleavable ester, oligomeric ester,        ether, carbonate, and orthoester substituents.

In preferred R^(CL*) substituents:

-   -   r* is 1 or 2;    -   L^(1*) is selected from C₁-C₁₂ alkylene, particularly C₁-C₆        alkylene, and heteroatom-containing C₁-C₁₂ alkylene;    -   X* is C₃-C₁₈ alicyclic, more preferably C₆-C₁₂ alicyclic;    -   L^(2*) is selected from C₁-C₁₂ alkylene, hydroxyl-substituted        C₁-C₁₂ alkylene, C₁-C₁₂ lene, and hydroxyl-substituted C₁-C₁₂        fluoroalkylene; and    -   R^(1*) is selected from —(CO)—O—R^(4*),        -[Q^(1*)—(CO)—O—]_(h*)—R^(5*), —O—R^(6*), and —R^(7*);    -   h* is an integer in the range of 2 to 8 inclusive,    -   Q^(1*) is C₁-C₁₂ alkylene or C₁-C₁₂ fluoroalkylene,    -   R^(4*) and R^(6*) are selected from (a) hydrocarbyl substituents        with a tertiary carbon attachment point, (b) substituents having        the structure —CR^(8*)R^(9*)—O—CR^(10*)R^(11*)R^(12*), and (c)        substituents having the structure —CR¹³*(OR¹⁴*)₂;    -   R^(5*), R^(7*), and R^(14*) are selected from C₄-C₁₂        hydrocarbyl, substituted C₄-C₁₂ hydrocarbyl,        heteroatom-containing C₄-C₁₂ hydrocarbyl, and substituted        heteroatom-containing C₄-C₁₂ hydrocarbyl; and    -   R^(8*), R^(9*), R^(10*), R^(11*), R^(12*), and R^(13*) are        independently selected from hydrogen, C₄-C₁₂ hydrocarbyl,        substituted C₄-C₁₂ hydrocarbyl, heteroatom-containing C₄-C₁₂        hydrocarbyl, and substituted heteroatom-containing C₄-C₁₂        hydrocarbyl, and further wherein any two of R^(8*), R^(9*),        R^(10*), R^(11*), and R^(12*) may be linked to form a cyclic        group.

Preferably, L^(2*) is of the formula —CR^(9*)R^(10*)—, wherein R^(9*) ishydrogen, C₁-C₁₂ alkyl, or C₁-C₁₂ fluoroalkyl, and R^(10*) is C₁-C₁₂alkyl or C₁-C₁₂ fluoroalkyl; and R^(4*), R^(5*), R^(6*), R^(7*), and R⁸*are independently selected from hydrogen, C₄-C₁₂ hydrocarbyl,substituted C₄-C₁₂ hydrocarbyl, heteroatom-containing C₄-C₁₂hydrocarbyl, and substituted heteroatom-containing C₄-C₁₂ hydrocarbyl,and further wherein any two of R^(4*), R^(5*), R^(6*), R^(7*), and R⁸may be linked to form a cyclic group.

R^(4*) and R^(6*) may further be selected from cyclic and acyclichydrocarbyl substituents with a tertiary carbon attachment point.Specific groups include, without limitation, t-butyl,2-methyl-2-norbornyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl,isobornyl, 2-methyl-2-isobornyl, 2-methyl-2-tetracyclododecyl,1-methylcyclohexyl, 1-ethylcyclohexyl, 1-butylcyclohexyl,1-methylcyclopentyl, 1-ethylcyclopentyl, and 1-butylcyclopentyl.

The polar substituent R^(P) may be, for example, an anhydride, lactone,imide, fluoroalcohol, carboxylic acid, sulfonamide, or the like.Although not limited thereto, the polar substituent R^(P) may have thestructure (VIII):-(L³)_(m1)—(Y)_(n1)—(L⁴)_(q1)—R¹⁸  (VIII)

-   -   in which m1, n1, and q1 are independently zero or 1;    -   L³ is defined as for L¹, i.e., L³ is selected from C₁-C₁₂        alkylene, substituted C₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene,        substituted C₁-C₁₂ heteroalkylene, and further wherein when L³        is optionally substituted and/or heteroatom-containing C₃-C₁₂        alkylene, L¹ may be linear, branched, or cyclic;    -   Y is defined as for X, i.e., Y is selected from C₃-C₃₀ alicyclic        and substituted C₃-C₃₀ alicyclic;    -   L⁴ is defined as for L², i.e., L⁴ is selected from C₁-C₁₂        alkylene, substituted C₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene,        substituted C₁-C₁₂ heteroalkylene; preferably, C₁-C₁₂ alkylene,        hydroxyl-substituted C₁-C₁₂ alkylene, C₁-C₁₂ fluoroalkylene, and        hydroxyl-substituted C₁-C₁₂ fluoroalkylene; and further wherein        when L⁴ is optionally substituted and/or heteroatom-containing        C₃-C₁₂ alkylene, L⁴ may be linear, branched, or cyclic; and    -   R¹⁸ is an acid-inert, polar organic group containing a        heteroatom with a Pauling electronegativity greater than about        3.00.

Preferred such acid-inert, polar substituents R^(P) are those wherein:

-   -   L³ is selected from C₁-C₁₂ alkylene, particularly C₁-C₆        alkylene, and heteroatom-containing C₁-C₁₂ alkylene;    -   Y is C₃-C₁₈ alicyclic, particularly C₆-C₁₂ alicyclic; and    -   Preferably, L⁴ is of the formula —CR²¹CR²²— wherein R²¹ is        hydrogen, C₁-C₁₂ alkyl, or C₁-C₁₂ fluoroalkyl, and R²² is C₁-C₁₂        alkyl or C₁-C₁₂ fluoroalkyl.

The heteroatom of R¹⁸ is preferably O or N. Although not limitedthereto, exemplary R¹⁸ groups include hydroxyl, carboxyl, C₁-C₁₂ alkoxy,C₁-C₁₂ fluoroalkoxy, hydroxyl-substituted C₁-C₁₂ alkoxy,hydroxyl-substituted C₁-C₁₂ fluoroalkoxy, C₂-C₁₂ alkoxyalkyl,fluorinated C₂-C₁₂ alkoxyalkyl, hydroxyl-substituted C₂-C₁₂ alkoxyalkyl,fluorinated hydroxyl-substituted C₂-C₁₂ alkoxyalkyl,hydroxyl-substituted C₁-C₁₂ alkyl, hydroxyl-substituted C₁-C₁₂fluoroalkyl, carboxyl-substituted C₁-C₁₂ alkyl, carboxyl-substitutedC₁-C₁₂ fluoroalkyl, C₂-C₁₂ acyl, fluorinated C₂-C₁₂ acyl,hydroxyl-substituted C₂-C₁₂ acyl, fluorinated hydroxyl-substitutedC₂-C₁₂ acyl, C₂-C₁₂ acyloxy, fluorinated C₂-C₁₂ acyloxy,hydroxyl-substituted C₂-C₁₂ acyloxy, fluorinated hydroxyl-substitutedC₂-C₁₂ acyloxy, amino, mono- and di-(C₁-C₁₂ alkyl)-substituted amino,amido, mono- and di-(C₂-C₁₂ alkyl)amido, sulfonamido, N-heteroalicyclic,oxo-substituted N-heterocyclic, and, where the substituents permit,combinations of two or more of the foregoing.

Representative preferred polar substituents R^(P) include lactone,anhydride, sulfonamide, fluoroalkanol, alkanol, alicyclic alkanol,esters, ethers, and a combination thereof.

In another aspect, the polymer may contain at least one acid-inert,non-polar substituent R^(NP). Exemplary such groups, without limitation,may be selected from C₁-C₁₈ hydrocarbyl and substituted C₁-C₁₈hydrocarbyl, e.g., fluorinated C₁-C₁₈ hydrocarbyl. Acid-inert R^(NP)moieties include, by way of example, C₁-C₁₈ alkyl, C₁-C₁₈ hydroxyalkyl,fluorinated C₁-C₁₈ alkyl, and fluorinated C₁-C₁₈ hydroxyalkyl. Examplesof fluorinated hydroxyalkyl groups include, without limitation,fluorinated lower alkanol groups having the structure-(L)_(x)-CQ¹Q²⁻-OH, wherein x is zero or 1, L is a linker (e.g., L¹ orL² as defined earlier herein), Q¹ is F or CF₃, and Q² is H, F, or CF₃.

In another aspect of the invention, at least one additional polymer maybe combined with the polymer to form a blend composition, includingfluorine-containing or non-fluorine containing polymers.

III. Photoresist Compositions

In another embodiment, a photoresist composition is provided thatcomprises both the inventive polymer, as described in detail above, anda photoacid generator, with the polymer representing up to about 99 wt.% of the solids included in the composition, and the photoacid generatorrepresenting approximately 0.1 to 25 wt. % of the solids contained inthe composition. Other components and additives may also be present,e.g., dissolution modifying additives such as dissolution inhibitors.

The photoacid generator may be any compound that, upon exposure toradiation, generates a strong acid and is compatible with the othercomponents of the photoresist composition. Examples of preferredphotochemical acid generators (PAGs) include, but are not limited to,sulfonates, onium salts, aromatic diazonium salts, sulfonium salts,diaryliodonium salts and sulfonic acid esters of N-hydroxyamides orN-hydroxyimides, as disclosed in U.S. Pat. No. 4,731,605. Any PAG(s)incorporated into the present photoresists should have high thermalstability, i.e., stable to at least 140° C., so they are not degradedduring pre-exposure processing.

Any suitable photoacid generator can be used in the photoresistcompositions of the invention. Typical photoacid generators include,without limitation:

-   -   (1) sulfonium salts, such as triphenylsulfonium        perfluoromethanesulfonate (triphenylsulfonium triflate),        triphenylsulfonium perfluorobutanesulfonate, triphenylsulfonium        perfluoropentanesulfonate, triphenylsulfonium        perfluorooctanesulfonate, triphenylsulfonium        hexafluoroantimonate, triphenylsulfonium hexafluoroarsenate,        triphenylsulfonium hexafluorophosphate, triphenylsulfonium        bromide, triphenylsulfonium chloride, triphenylsulfonium iodide,        2,4,6-trimethylphenyldiphenylsulfonium perfluorobutanesulfonate,        2,4,6-trimethylphenyldiphenylsulfonium benzenesulfonate,        tris(t-butylphenyl)sulfonium perfluorooctane sulfonate,        diphenylethylsulfonium chloride, and phenacyldimethylsulfonium        chloride;    -   (2) halonium salts, particularly iodonium salts, including        diphenyliodonium perfluoromethanesulfonate (diphenyliodonium        triflate), diphenyliodonium perfluorobutanesulfonate,        diphenyliodonium perfluoropentanesulfonate, diphenyliodonium        perfluorooctanesulfonate, diphenyliodonium hexafluoroantimonate,        diphenyliodonium hexafluoroarsenate, bis-(t-butylphenyl)iodonium        triflate, and bis-(t-butylphenyl)-iodonium camphanylsulfonate;    -   (3) α,α′-bis-sulfonyl-diazomethanes such as        bis(p-toluenesulfonyl)diazomethane, methylsulfonyl        p-toluenesulfonyldiazomethane,        1-cyclohexylsulfonyl-1-(1,1-dimethylethylsulfonyl) diazomethane,        and bis(cyclohexylsulfonyl)diazomethane;    -   (4) trifluoromethanesulfonate esters of imides and        hydroxyimides, e.g.,        α-(trifluoromethylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide        (MDT);    -   (5) nitrobenzyl sulfonate esters such as 2-nitrobenzyl        p-toluenesulfonate, 2,6-dinitrobenzyl p-toluenesulfonate, and        2,4-dinitrobenzyl p-trifluoromethylbenzene sulfonate;    -   (6) sulfonyloxynaphthalimides such as        N-camphorsulfonyloxynaphthalimide and        N-pentafluorophenylsulfonyloxynaphthalimide;    -   (7) pyrogallol derivatives (e.g., trimesylate of pyrogallol);    -   (8) naphthoquinone-4-diazides;    -   (9) alkyl disulfones;    -   (10) s-triazine derivatives, as described in U.S. Pat. No.        4,189,323; and    -   (10) miscellaneous sulfonic acid generators including        t-butylphenyl-α-(p-toluenesulfonyloxy)-acetate,        t-butyl-α-(p-toluenesulfonyloxy)acetate, and        N-hydroxy-naphthalimide dodecane sulfonate (DDSN), and benzoin        tosylate.

Other suitable photoacid generators are disclosed in Reichmanis et al.(1991), Chemistry of Materials 3:395, and in U.S. Pat. No. 5,679,495 toYamachika et al. Additional suitable acid generators useful inconjunction with the compositions and methods provided herein will beknown to those skilled in the art and/or are described in the pertinentliterature.

A dissolution modifying additive, generally although not necessarily adissolution inhibitor, is typically included. If a dissolution inhibitoris present, it will typically represent in the range of about 1 wt. % to40 wt. %, preferably about 5 wt. % to 30 wt. %, of the total solids.

Preferred dissolution inhibitors have high solubility in the resistcomposition and in the solvent used to prepare solutions of the resistcomposition (e.g., propylene glycol methyl ether acetate, or “PGMEA”),exhibit strong dissolution inhibition, have a high exposed dissolutionrate, are substantially transparent at the wavelength of interest, mayexhibit a moderating influence on T_(g), strong etch resistance, anddisplay good thermal stability (i.e., stability at temperatures of about140° C. or greater). Suitable dissolution inhibitors include, but arenot limited to, bisphenol A derivatives, e.g., wherein one or bothhydroxyl moieties are converted to a t-butoxy substituent or aderivative thereof such as a t-butoxycarbonyl or t-butoxycarbonylmethylgroup; fluorinated bisphenol A derivatives such as CF₃-bisphenolA-OCH₂(CO)—O-tBu (6F-bisphenol A protected with a t-butoxycarbonylmethylgroup); normal or branched chain acetal groups such as 1-ethoxyethyl,1-propoxyethyl, 1-n-butoxyethyl, 1-isobutoxy-ethyl, 1-t-butyloxyethyl,and 1-t-amyloxyethyl groups; and cyclic acetal groups such astetrahydrofuranyl, tetrahydropyranyl, and 2-methoxytetrahydro-pyranylgroups; androstane-17-alkylcarboxylates and analogs thereof, wherein the17-alkylcarboxylate at the 17-position is typically lower alkyl.Examples of such compounds include lower alkyl esters of cholic,ursocholic and lithocholic acid, including methyl cholate, methyllithocholate, methyl ursocholate, t-butyl cholate, t-butyl lithocholate,t-butyl ursocholate, and the like (see, e.g., Allen et al. (1995) J.Photopolym. Sci. Technol., cited supra); hydroxyl-substituted analogs ofsuch compounds (ibid.); and androstane-17-alkylcarboxylates substitutedwith one to three C₁-C₄ fluoroalkyl carbonyloxy substituents, such ast-butyl trifluoroacetyllithocholate (see, e.g., U.S. Pat. No. 5,580,694to Allen et al.).

The remainder of the resist composition is composed of a solvent and mayadditionally, if necessary or desirable, include customary additivessuch as dyes, sensitizers, additives used as stabilizers, dissolutionmodifying additives, and acid-diffusion controlling agents, basiccompounds, coating aids such as surfactants or anti-foaming agents,crosslinking agents, photospeed control agents, adhesion promoters andplasticizers.

The choice of solvent is governed by many factors not limited to thesolubility and miscibility of resist components, the coating process,and safety and environmental regulations. Additionally, inertness toother resist components is desirable. It is also desirable that thesolvent possess the appropriate volatility to allow uniform coating offilms yet also allow significant reduction or complete removal ofresidual solvent during the post-application bake process. See, e.g.,Introduction to Microlithography, Eds. Thompson et al., citedpreviously. In addition to the above components, the photoresistcompositions provided herein generally include a casting solvent todissolve the other components so that the overall composition may beapplied evenly on the substrate surface to provide a defect-freecoating. Where the photoresist composition is used in a multilayerimaging process, the solvent used in the imaging layer photoresist ispreferably not a solvent to the underlayer materials, otherwise theunwanted intermixing may occur. The invention is not limited toselection of any particular solvent. Suitable casting solvents maygenerally be chosen from ether-, ester-, hydroxyl-, andketone-containing compounds, or mixtures of these compounds. Examples ofappropriate solvents include carbon dioxide, cyclopentanone,cyclohexanone, ethyl 3-ethoxypropionate (EEP), a combination of EEP andγ-butyrolactone (GBL), lactate esters such as ethyl lactate, alkyleneglycol alkyl ether esters such as PGMEA, alkylene glycol monoalkylesters such as methyl cellosolve, butyl acetate, and 2-ethoxyethanol.Preferred solvents include ethyl lactate, propylene glycol methyl etheracetate, ethyl 3-ethoxypropionate and their mixtures. The above list ofsolvents is for illustrative purposes only and should not be viewed asbeing comprehensive nor should the choice of solvent be viewed aslimiting the invention in any way. Those skilled in the art willrecognize that any number of solvents or solvent mixtures may be used.

Greater than 50 percent of the total mass of the resist formulation istypically composed of the solvent, preferably greater than 80 percent.

Other customary additives include dyes that may be used to adjust theoptical density of the formulated resist and sensitizers which enhancethe activity of photoacid generators by absorbing radiation andtransferring it to the photoacid generator. Examples include aromaticssuch as functionalized benzenes, pyridines, pyrimidines, biphenylenes,indenes, naphthalenes, anthracenes, coumarins, anthraquinones, otheraromatic ketones, and derivatives and analogs of any of the foregoing.

A wide variety of compounds with varying basicity may be used asstabilizers and acid-diffusion controlling additives. They may includenitrogenous compounds such as aliphatic primary, secondary, and tertiaryamines, cyclic amines such as piperidines, pyrimidines, morpholines,aromatic heterocycles such as pyridines, pyrimidines, purines, iminessuch as diazabicycloundecene, guanidines, imides, amides, and others.Ammonium salts may also be used, including ammonium, primary, secondary,tertiary, and quaternary alkyl- and arylammonium salts of alkoxidesincluding hydroxide, phenolates, carboxylates, aryl and alkylsulfonates, sulfonamides, and others. Other cationic nitrogenouscompounds including pyridinium salts and salts of other heterocyclicnitrogenous compounds with anions such as alkoxides including hydroxide,phenolates, carboxylates, aryl and alkyl sulfonates, sulfonamides, andthe like may also be employed. Surfactants may be used to improvecoating uniformity, and include a wide variety of ionic and non-ionic,monomeric, oligomeric, and polymeric species. Likewise, a wide varietyof anti-foaming agents may be employed to suppress coating defects.Adhesion promoters may be used as well; again, a wide variety ofcompounds may be employed to serve this function. A wide variety ofmonomeric, oligomeric, and polymeric plasticizers such as oligo- andpolyethyleneglycol ethers, cycloaliphatic esters, and non-acid reactivesteroidally derived materials may be used as plasticizers, if desired.However, neither the classes of compounds nor the specific compoundsmentioned above are intended to be comprehensive and/or limiting. Oneversed in the art will recognize the wide spectrum of commerciallyavailable products that may be used to carry out the types of functionsthat these customary additives perform.

Typically, the sum of all customary additives will comprise less than 20percent of the solids included in the resist formulation, preferably,less than 5 percent.

The photoresist compositions of the invention may also contain polymersselected to provide or increase certain properties, such as transparencyat a predetermined, desired wavelength, increase dry etch resistance,and/or improve aqueous base development. Representative such polymersare disclosed in published U.S. Patent Application 2003/0171490 A1 toBreyta et al., for “Polymer Blend and Associated Methods of Preparationand Use,” assigned to International Business Machines Corporation.Polymers that are non-fluorine-containing or fluorine-containing may beused. Of the latter, preferred polymers contain monomer units bearing afluoroalcohol group, such as NBHFA(bicyclo[2.2.1]hept-5-ene-2-(1,1,1-trifluoro-2-trifluoromethylpropan-2-ol).These polymers may be NBHFA homopolymers (“PNBHFA”) or copolymers ofNBHFA with other monomers, including, without limitation, othernorbornene monomers.

IV. Use in Generation of Resist Images on a Substrate

The present invention also relates to a process for generating a resistimage on a substrate. In general, the process involves: (a) coating asubstrate with a film of a photoresist composition provided herein; (b)patternwise exposing the film to an imaging radiation source so as toform a latent, patterned image in the film; (c) baking the exposed filmat a post-exposure bake temperature below about 100° C.; and (d)developing the latent image with a developer to form a patternedsubstrate.

The first step involves coating the substrate with a film comprising theresist composition dissolved in a suitable solvent. Suitable substratesare ceramic, metallic or semiconductive, and preferred substrates aresilicon-containing, including, for example, silicon dioxide, siliconnitride, and silicon oxynitride. The substrate may or may not be coatedwith an organic anti-reflective layer prior to deposition of the resistcomposition.

Preferably, the surface of the substrate is cleaned by standardprocedures before the film is deposited thereon. Suitable solvents forthe composition are as described previously herein, and include, forexample, cyclohexanone, ethyl lactate, and propylene glycol methyl etheracetate. The film can be coated on the substrate using art-knowntechniques such as spin or spray coating, or doctor blading. Preferably,before the film has been exposed to radiation, the film may be subjectedto a prebake step at a temperature and for a time sufficient to removeresidual solvent. Such prebake temperatures are generally in the rangeof about 90-150° C., preferably below about 130° C., more typically inthe range of about 80-120° C., for a short period of time, typically onthe order of about 1 minute. The dried film has a thickness of about0.02 to 5.0 microns, preferably about 0.05 to 2.5 microns, and mostpreferably about 0.10 to 1.0 microns. The radiation may be ultraviolet,electron beam or x-ray. Ultraviolet radiation is preferred, particularlydeep ultraviolet radiation having a wavelength of less than about 250nm, e.g., 157 nm using an F₂ excimer laser. The radiation is absorbed bythe radiation-sensitive acid generator to generate free acid, which withheating causes cleavage of the acid-labile pendant groups and formationof the corresponding acid.

The “post-exposure bake” (PEB) processing is carried out by baking theexposed film at a post-exposure bake temperature below about 100° C.,and typically in the range of about 25° C. to about 100° C. Preferably,the PEB is carried out at a temperature in the range of about 25° C. toabout 80° C., more preferably at a temperature in the range of about 25°C. to about 50° C.

The fourth step involves development of the image with a suitablesolvent. Suitable solvents include an aqueous base, preferably anaqueous base without metal ions such as the industry standard developertetramethylammonium hydroxide or choline. Other solvents may includeorganic solvents or carbon dioxide (in the liquid or supercriticalstate), as disclosed in U.S. Pat. No. 6,665,527 to Allen et al. Theresist composition may be used with DUV wavelengths of 157 nm, 193 nm,or 248 nm, or with EUV (e.g., at 13 nm), electron beam or x-rayradiation.

In the manufacture of integrated circuits, circuit patterns can beformed in the exposed areas after resist development by coating thesubstrate with a conductive material, e.g., a metallic material, usingknown techniques such as evaporation, sputtering, plating, chemicalvapor deposition, or laser-induced deposition. Dielectric materials mayalso be deposited by similar means during the process of makingcircuits. Inorganic ions such as boron, phosphorous, or arsenic can beimplanted in the substrate in the process for making p-doped or n-dopedcircuit transistors. Examples of such processes are disclosed in U.S.Pat. Nos. 4,855,017, 5,362,663, 5,429,710, 5,562,801, 5,618,751,5,744,376, 5,801,094, and 5,821,469. Other examples of pattern transferprocesses are described in Chapters 12 and 13 of Moreau, SemiconductorLithography, Principles, Practices, and Materials (Plenum Press, 1988).It should be understood that the invention is not limited to anyspecific lithographic technique or device structure.

It is to be understood that while the invention has been described inconjunction with the preferred specific embodiments thereof, that theforegoing description as well as the examples that follow are intendedto illustrate and not limit the scope of the invention. Other aspects,advantages and modifications within the scope of the invention will beapparent to those skilled in the art to which the invention pertains.

All patents, patent applications, and publications mentioned herein arehereby incorporated by reference in their entireties.

EXAMPLES

The following examples are intended to provide those of ordinary skillin the art with a complete disclosure and description of how to prepareand use the compositions disclosed and claimed herein. Efforts have beenmade to ensure accuracy with respect to numbers (e.g., amounts,temperature, etc.), but allowance should be made for the possibility oferrors and deviations. Unless indicated otherwise, parts are parts byweight, temperature is in °C and pressure is at or near atmospheric.Additionally, all starting materials were obtained commercially or weresynthesized using known procedures.

Where appropriate, the following techniques and equipment were utilizedin the Examples: ¹H and ¹³C NMR spectra were obtained at roomtemperature on an Avance 400 spectrometer. Quantitative ¹³C NMR was runat room temperature in acetone-d₆ in an inverse-gated ¹H-decoupled modeusing Cr(acac)₃ as a relaxation agent on an Avance 400 spectrometer. Forpolymer composition analysis ¹⁹F NMR (379 MHz) spectra were alsoobtained using a Bruker Avance 400 spectrometer. Thermo-gravimetricanalysis (TGA) was performed at a heating rate of 5° C./min in N₂ on aTA Instrument Hi-Res TGA 2950 Thermogravimetric Analyzer. Differentialscanning calorimetry (DSC) was performed at a heating rate of 10° C./minon a TA Instruments DSC 2920 modulated differential scanningcalorimeter. Molecular weights were measured in tetrahydrofuran (THF) ona Waters Model 150 chromatograph relative to polystyrene standards. IRspectra were recorded on a Nicolet 510 FT-IR spectrometer on a film caston a KBr plate. UV measurements at 157 nm were performed using a VarianCary Model 400 spectrometer on multiple thickness on CaF₂ discs. Filmthickness was measured on a Tencor alpha-step 2000. A quartz crystalmicrobalance (QCM) was used to study the dissolution kinetics of theresist films in an aqueous tetramethylammonium hydroxide (TMAH) solution(CD-26). Contact angles were measured on an AST Products VCA 2500XEvideo contact angle system using 2 μL of filtered deionized water.

Example 1 Synthesis of Ethoxymethyl Methacrylate (EMMA)

To a 500-mL, 3-necked round bottomed flask equipped with a thermocoupletemperature monitor, 250-mL addition funnel, nitrogen inlet and amagnetic stirrer was added 150 mL of dichloromethane, and 18.9 g (0.22mol) of methacrylic acid. The addition funnel was charged with a mixtureof 22.3 g (0.23 mol) of triethylamine and 25 mL of dichloromethane whichwas then added in a thin stream to the flask with stirring in anice-bath. Upon completion of the addition, the addition funnel wasrecharged with a mixture of 18.9 g (0.2 mol) of chloromethyl ethyl etherand 25 mL of dichloromethane which was subsequently added dropwise tothe reaction mixture with cooling over about 15 minutes. The ice bathwas removed and the mixture stirred at room temperature overnight. Theresulting suspension was filtered and the filtrate washed several timeswith saturated bicarbonate, water and brine and dried over anhydrousmagnesium sulfate. Filtration and removal of the solvent by evaporationon a rotary evaporator provided 26.1 g of a yellowish oil which wasdistilled at reduced pressure to provide 20.3 g (70%) of the titlecompound as a clear, colorless oil.

Example 2 Synthesis of 2-Ethoxy-2-ethyl Methacrylate (EEMA)

To a 500-mL, 3-necked round bottomed flask equipped with a thermocoupletemperature monitor, nitrogen inlet and a magnetic stirrer was added 300mL of ethyl vinyl ether and 25.0 g (0.29 mol) of methacrylic acid. Themixture was cooled in an ice bath and 0.2 g (0.001 mol) ofp-toluenesulfonic acid monohydrate was added. The flask was removed fromthe ice bath and stirred for 4 hours at which time the mixture wasfiltered through a bed of sodium carbonate and the ethyl vinyl etherremoved on a rotary evaporator. The resulting oil was distilled twicefrom sodium carbonate at reduced pressure to yield 8.9 g (20%) of thetitle compound as a clear, colorless oil.

Example 3 Synthesis of 2-Ethoxy-2-ethyl Trifluoromethacrylate (EETFMA)

14.0 g of 2-trifluoromethylacrylic acid (2-TFMAA) and 30 g of ethylvinyl ether were stirred at room temperature under nitrogen and using aDRY ICE condenser. The initial endotherm gave way to a mild exotherm toapproximately 33° C. and some outgassing (reflux). The reaction wascomplete in 15 minutes. Et₂O added. Organics were washed with 10% Na₂CO₃(containing a small amount of NaOH), saturated NaHCO₃ and finally brinefollowed by drying with MgSO₄. Evaporated on rotary evaporator at 30° C.Yield 29.0 g of colorless liquid.

Example 4 Synthesis of 2-Tetrahydrofuranyl Methacrylate (THFMA)

To a 500-mL, 3-necked round bottomed flask equipped with a thermocoupletemperature monitor, nitrogen inlet and a magnetic stirrer was added 300mL of dichloromethane, 24.5 g (0.29 mol) of methacrylic acid and 21.4 g(0.305 mol) of 2,3-dihydrofuran. The flask was cooled under Nitrogen to−40° C. and 0.05 g of methanesulfonic acid was added. The mixture waswarmed to 0° C. and stirred for 6 hours at which time it was recooled to−40° C. and an excess (1 mL) of triethylamine was added. The solutionwas then washed with saturated sodium bicarbonate, water and brine anddried over anhydrous magnesium sulfate. Distillation from sodiumcarbonate at reduced pressure resulted in 26 g (58%) of the titlecompound.

Example 5 Synthesis of 2-Tetrahydropyranyl Methacrylate (THPMA)

2-Tetrahydropyranyl methacrylate (THPMA) was prepared in an analogousmanner to the THF-ester above using 24.5 g (0.29 mol) of methacrylicacid, 25.6 g (0.305 mol) of 4,5-dihydropyran and 0.05 g ofmethanesulfonic acid to yield 35.5 g (72%) of the desired product afterdistillation at reduced pressure.

Example 6 Synthesis of 2-Tetrahydrofuranyl Trifluoromethacrylate(THFTFMA)

2-Tetrahydrofuranyl trifluoromethacrylate (THFTFMA) was prepared in amanner analogous to EETFMA but using water bath cooling. Yield of 18.2 g(87%) of a clear liquid from 14.0 g of 2-TFMAA and 14.0 g of2,3-dihydrofuran.

Example 7 Synthesis of α-Angelicalactone Methacrylate (ALMA)

α-Angelicalactone (29.54 g, 0.30 mole), methacrylic acid (20.66 g, 0.24mole), p-toluenesulfonic acid monohydrate (200 mg), and phenothiazine(100 mg) were placed in a round bottom flask equipped with a magneticstirbar, a water condenser and a nitrogen inlet. The contents werestirred at room temperature. Within about 5 minutes, the reaction becameexothermic. The flask was immersed in an ice-bath and stirred for 30minutes. Afterwards, the ice-bath was removed and stirred at roomtemperature for 1 hour. The solution was diluted with 150 ml of etherand treated with 1 ml ammonium hydroxide (28% ammonia in water). Someprecipitation occurred. The solution was filtered through a flutedfilter paper and washed with 2×150 ml saturated sodium bicarbonatesolution followed by 1×150 ml brine and dried over anhydrous magnesiumsulfate for about an hour. The solvent was removed on a rotaryevaporator and distilled under reduced pressure to yield 22.2 grams ofthe product which was collected between 83° C. and 93° C. at 0.2 mmpressure.

Example 8 Synthesis of α-Angelicalactone Acrylate (ALA)

α-Angelicalactone Acrylate was prepared by a method identical to thatdescribed for ALMA. Starting with α-Angelicalactone (19.62 g, 0.20 mole)and acrylic acid (10.80 g, 0.15 mole), 10.3 grams of ALA was collectedbetween 75° C. and 85° C. at 0.2 mm Hg.

Example 9 Synthesis of3-(5-Bicyclo-[2,2,1]hept-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)-2-propanolMethacrylate (NBHFAMA)

3-(5-Bicyclo-[2,2,1]heptene-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)-2-propanol(NBHFA) (Central Glass, Japan) (54.8 g, 0.20 mole), methacrylic acid(51.65 g, 0.60 mole) and 50 ml of ether were placed in a round bottomflask equipped with a condenser, magnetic stirrer and a nitrogen inlet.While stirring, concentrated sulfuric acid 96% (6.08 g, 3.25 ml, 0.06mole) was added dropwise at room temperature via a graduated pipette. Amildly exothermic reaction occurred. The mixture was heated to refluxfor 18 hours. Afterwards, the mixture was diluted with 50 mltetrahydrofuran (THF) and poured cautiously into a sodium bicarbonatesolution (50 grams, 0.60 mole in 600 ml DI water) and stirred for 2hours. The mixture was then extracted with 2×150 ml ether. Combinedorganic extracts were washed with 150 ml of a saturated sodiumbicarbonate solution followed by 150 ml of brine and dried overanhydrous magnesium sulfate. The solution was concentrated in vacuo.Fractional distillation under reduced pressure gave 32.44 grams of thedesired product at 140° C. at 2 mm Hg.

Example 10 Synthesis of3-(5-Bicyclo-[2,2,1]hept-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)-2-propanolAcrylate (NBHFAA)

The acrylate monomer was synthesized using a procedure similar to theone utilized for NBHFAMA.

Example 11 Synthesis of Copoly(NBHFAMA/EMMA) 60/40

To a 100-mL, 3-necked round-bottomed flask equipped with a condenser,nitrogen inlet, temperature monitor, heating mantle and magnetic stirrerwas added 9.4 g (0.027 mol) of3-(5-Bicyclo-[2,2,1]hept-2-yl)-1,1,1-trifluoro-2-(trifluoromethyl)-2-propanolmethacrylate (NBHFAMA), 2.53 g (0.018 mol) of EMMA and 38 mL of THF andthe mixture heated to near reflux at which time 0.432 g (0.0026 mol) ofAIBN was added and the mixture stirred at reflux for six hours. Thepolymer product was isolated by precipitation from 3 L of hexane anddrying at reduced pressure in a vacuum oven at 50° C.

Example 12 Synthesis of Copoly(NBHFAMA/EEMA) 60/40

The copolymer copoly(NBHFAMA/EEMA) was prepared in an analogous fashionto the above EMMA polymer using 9.28 g (0.026 mol) of NBHFAMA and 2.72 g(0.0172 mol) of EEMA and 0.43 g of AIBN.

Example 13 Synthesis of Copoly(NBHFA/THFMA) 60/40

To a 100-mL, 3-necked round-bottomed flask equipped with a condenser,nitrogen inlet, temperature monitor, heating mantle and magnetic stirrerwas added 9.3 g (0.026 mol) of NBHFAMA, 2.7 g (0.0172 mol) of THFMA and38 mL of methyl acetate and the mixture heated to near reflux at whichtime 0.382 g (0.00172 mol) of VASO-52 was added and the mixture stirredat reflux for six hours and at room temperature overnight. The polymerproduct was isolated by precipitation from 3 L of hexane and drying atreduced pressure in a vacuum oven at 50° C.

FIG. 3 depicts contrast curves for a resist material prepared for theNBHFA/THFMA copolymer of this Example. In FIG. 3, the effect of dose onthe resist thickness was determined for various post exposure baketemperatures (PEB) and a post applied bake (PAB) of 60 sec. at 130° C.

In FIG. 4, an SEM photomicrograph of the resist of this Example is shownfor a PEB of 50° C. and a dose of 50.4 mJ/cm².

Example 14 Synthesis of Copoly(NBHFAMA/THPMA) 60/40

The copolymer copoly(NBHFAMA/THPMA) 60/40 was prepared in an analogousfashion to the THFMA polymer above using 9.3 g (0.026 mol) of NBHFAMA,2.94 g (0.0172 mol) of THPMA.

Example 15 Synthesis of Copoly(NBHFAMA/ALMA) 50:50

NBHFAMA (3.60 grams, 0.01 mole), ALMA (1.84 grams, 0.01 mole) and 16grams of tetrahydrofuran (THF) were placed in a round bottom flaskequipped with a condenser and a nitrogen inlet.2,2′-Azobisisobutyronitrile (AIBN) (0.13 grams, 0.0008 mole) was addedto this solution and stirred until dissolved. The solution was thendegassed using four vacuum/nitrogen purges. The contents were thenheated to reflux for 18 hours. Afterwards, the solution was addeddropwise into hexanes (500 ml). The precipitated polymer was filtered(frit), washed twice with hexanes (50 ml) and dried under vacuum at 60°C. Yield: 4.9 grams. Mn=13,900. Polydispersity: 2.4. Tg: 145° C.

Example 16 Synthesis of Terpoly(NBHFA/NBHFAA/ALA) 50:25:25

NBHFA (5,48 g, 0.02 mole), NBHFAA (3.46 grams, 0.01 mole), ALA (1.70grams, 0.01 mole) and 11 grams of ethylacetate were placed in a roundbottom flask equipped with a condenser and a nitrogen inlet.2,2′-Azobisisobutyronitrile (AIBN) (0.26 grams, 0.0016 mole) was addedto this solution and stirred until dissolved. Then, the solution wasdegassed using four vacuum/nitrogen purges. The contents were thenheated to reflux for 18 hours. Afterwards, the solution was added dropwise into hexanes (600 ml). The precipitated polymer was filtered(frit), washed twice with hexanes (50 ml) and dried under vacuum at 60°C. Yield: 6.3 grams. Mn=4,885. Polydispersity: 2.3. Tg: 98° C.

Example 17 Synthesis of Terpoly(THPMA/NLM/IsoBuHFAMA) 45:40:15

THPMA (3.83 grams, 0.0225 mole),5-methacryloxy-2,6-norbornenecarbolactone (NLM, JSR Corp., Japan) (4.45grams, 0.02 mole), 1,1-bistrifluoromethyl-1-hydroxy-3-methylbut-4-ylmethacrylate (IsoBuHFAMA) (2.31 grams, 0.0074 mole), dodecanethiol(0.051 gram, 0.00025 mole), dimethyl-2,2′-azobisisobutyrate (V-601, WacoChemicals) and 34 grams of tetrahydrofuran was degassed 3 times withnitrogen/vacuum and heated to reflux under nitrogen for 4.5 hours. Thereaction mixture was cooled to room temperature and precipitated in 3.5liters of hexanes. The solid was collected, washed with three portionsof hexanes (150 mL), and dried under vacuum overnight at roomtemperature. Yield 8.5 grams. Mw=16.6 K Polydispersity 1.888. TGAmaximum decomposition rate in air at 147° C.

Example 18 Synthesis of Copoly(NBHFAMA/THPMA) 40:60

The copolymer copoly(NBHFAMA/THPMA) 40:60 was prepared in a similarfashion to the polymer above using 3.6 grams (0.010 mole) of NBHFAMA,2.53 grams (0.015 mole) of THPMA, 0.026 grams of dodecanethiol, 0.250grams of dimethyl-2,2′-azobisisobutyrate, and 17 grams of methylacetate. Yield: 5.1 grams. Mw=24.3 K Polydispersity 1.738. TGA maximumdecomposition rate in air at 155° C.

FIG. 5 depicts contrast curves for a resist material prepared for theTHPMA/NBHFAMA copolymer of this Example. In FIG. 5, the effect of doseon the resist thickness was determined for various post exposure baketemperatures (PEB) and a post applied bake (PAB) of 60 sec. at 90° C.

In FIG. 6, an SEM photomicrograph of the resist of this Example is shownfor a PEB of 80° C. and a dose of 31 mJ/cm².

Example 19 Synthesis of Copoly(IsoBuHFAMA/THPMA) 40:60

The copolymer copoly(IsoBuHFAMA/THPMA) 40:60 was prepared in a similarfashion to the polymer above using 3.6 grams (0.010 mole) of NBHFAMA,2.53 grams (0.015 mole) of THPMA, 0.026 grams of dodecanethiol, 0.239grams of Vaso 52, and 17 grams of methyl acetate. Yield: 4.43 grams.Mw=12.8 K Polydispersity 1.589. TGA maximum decomposition rate in air at135° C.

Example 20 Positive Resist Formulation

Copoly(NBHFAMA/ALMA) (50:50) (1.0 grams), and triphenylsulfoniumtriflate (30 mg) were dissolved in propylene glycol monomethyl etheracetate (PGMEA, 7 grams). Tetrabutylammonium hydroxide (0.3 ml of 1%solution in methanol) was added to this solution and filtered through a0.20 microns syringe filter.

Example 21 Positive Resist Evaluation

A silicon substrate was coated with 3000 Å of a positive resistcomposition (Example 20 above). The film was baked at 130° C. for 1minute to drive off the solvent. The film was then imagewise exposed at193 nm (dose 15-100 mJ/cm2). It was then baked at 80-90° C. for 1 minuteand developed with 0.263 N tetramethyl ammonium hydroxide. Highresolution images were obtained with this resist.

In FIGS. 1A and 1B, contrast curves for a NBHFAMA/ALMA 60/40 copolymerresist are depicted. In FIG. 1A, the contrast curves are shown for postapplied bake temperatures (PAB) in the range of 100-130° C. at a PEB of90° C.; in FIG. 1B, the contrast curves are shown for post exposure baketemperatures in the range of 68-88° C. at a PAB of 130° C.

(Note that in these Figures, and where relevant, all other Figures, thefollowing abbreviations apply: “Ex-FARM” refers to an extendedfluoroacrylate resist material; “OD” refers to optical density, in thiscase 193 nm; “CA” refers to the contact angle, 74.0 degrees; “NA” refersto numerical aperature; “L/S” refers to line spacing; “FT” refers tofilm thickness; “TGP” refers to thermal gradient plate; “COG” refers tochrome-on-glass; and “AL” refers to ALMA, i.e. angelicalactonemethacrylate).

In FIG. 2, the NBHFAMA/ALMA 60/40 copolymer was applied as a resistmaterial to a chrome-on-glass substrate, exposed at an OD of 193 nm and0.6 NA at line spacings of 110, 120 and 130 nm and aspect ratios of 1:1.The film thickness was 2600 Å.

1. A process for patterning a substrate, comprising: (a) coating thesubstrate with a film of a photoresist composition comprised of (i) apolymer that is rendered soluble in aqueous base at a temperature ofless than about 100° C. by acid-catalyzed deprotection of pendentacetal- or ketal-protected carboxylic acid groups, and (ii) a photoacidgenerator; (b) patternwise exposing the film to an imaging radiationsource so as to form a latent, patterned image in the film; (c) bakingthe exposed film at a post-exposure bake temperature below about 100°C.; and (d) developing the latent image with a developer to form apatterned substrate.
 2. The process of claim 1, wherein the radiation iselectron-beam, x-ray, ultraviolet, or extreme ultraviolet radiation. 3.The process of claim 2, wherein the radiation is ultraviolet radiation.4. The process of claim 3, wherein the ultraviolet radiation has awavelength of 193 nm, 157 nm, or 13.4 nm.
 5. The process of claim 4,wherein the ultraviolet radiation has a wavelength of 193 mm.
 6. Theprocess of claim 4, wherein the ultraviolet radiation has a wavelengthof 157 nm.
 7. The process of claim 1, further comprising etching thepatterned substrate.
 8. The process of claim 7, wherein the etchingcomprises ion etching.
 9. The process of claim 1, wherein the film isinsoluble in aqueous base, and wherein the imaging radiation renders thefilm soluble in the aqueous base where exposed to the imaging radiationsource.
 10. The process of claim 9, further comprising removing thesoluble portions of the film.
 11. The process of claim 1, wherein thesubstrate is ceramic, metallic, semiconductive, or a combinationthereof.
 12. The process of claim 1, wherein the substrate comprises asilicon wafer, a photolithographic mask blank, or a printed circuitboard.
 13. The process of claim 1, wherein the substrate comprisessilicon dioxide, silicon nitride, silicon oxynitride, or a combinationthereof.
 14. The process of claim 1, further comprising, before exposureof the film in (b), performing a prebake of the film at a temperatureand for a time sufficient to remove residual solvent.
 15. The process ofclaim 14, wherein the prebake temperature is below about 130° C.
 16. Theprocess of claim 1, wherein the post-exposure bake temperature isbetween about 25° C. and about 100° C.
 17. The process of claim 16,wherein the post-exposure bake temperature is between about 25° C. andabout 80° C.
 18. The process of claim 17, wherein the post-exposure baketemperature is between about 25° C. and about 50° C.
 19. The patternedsubstrate prepared by the process of claim
 1. 20. The process of claim1, wherein the polymer is prepared by polymerization of a monomermixture, the mixture comprising: (a) at least one first olefinic monomercontaining an acetal or ketal linkage, the acid-catalyzed cleavage ofwhich renders the polymer soluble in aqueous base; and (b) at least onesecond olefinic monomer selected from (i) an olefinic monomer containinga pendant fluorinated hydroxyalkyl group R^(H), (ii) an olefinic monomercontaining a pendant fluorinated alkylsulfonamide group R^(S), and (iii)combinations thereof.
 21. The process of claim 20, wherein the acetal orketal linkage is contained within an acid-cleavable group R^(CL) in thefirst olefinic monomer, the acid-cleavable group having the structure-(L¹)_(m)-(X)_(n)-(L²)_(q)-R¹  (I) in which: m, n, and q areindependently zero or 1; L¹ is selected from C₁-C₁₂ alkylene,substituted C₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂heteroalkylene, and further wherein when L¹ is optionally substitutedand/or heteroatom-containing C₁-C₁₂ alkylene, L¹ may be linear,branched, or cyclic; X is selected from C₃-C₃₀ alicyclic and substitutedC₃-C₃₀ alicyclic; L² is selected from C₁-C₁₂ alkylene, substitutedC₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂heteroalkylene, and further wherein when L² is optionally substitutedand/or heteroatom-containing C₃-C₁₂ alkylene, L² may be linear,branched, or cyclic; and R¹ is selected from acetal-containing andketal-containing substituents.
 22. The process of claim 20, wherein RHhas the structure -L³-CR¹¹R¹²—OH, in which: L³ is selected from C₁-C₁₂alkylene, substituted C₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene,substituted C₁-C₁₂ heteroalkylene, C₃-C₁₅ alicyclic, C₃-C₁₅fluoroalicyclic, and combinations thereof; R¹¹ is selected fromhydrogen, C₁-C₂₄ alkyl, and substituted C₁-C₂₄ alkyl; and R¹² is C₁-C₂₄alkyl or fluorinated C₁-C₂₄ alkyl, with the proviso that at least one ofR¹¹ and R¹² is fluorinated; and further wherein R¹¹ and R¹² can be takentogether to form a ring.
 23. The process of claim 20, wherein R^(S) hasthe structure -L³-SO₂—NHR¹⁶, in which: L³ is selected from C₁-C₁₂alkylene, substituted C₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene,substituted C₁-C₁₂ heteroalkylene, C₃-C₁₅ alicyclic, C₃-C₁₅fluoroalicyclic, combinations thereof, and R¹⁶ is selected from C₁-C₂₄alkyl and substituted C₁-C₂₄ alkyl, C₁-C₂₄ fluoroalkyl and substitutedC₁-C₂₄ fluoroalkyl.
 24. The process of claim 20, wherein the polymercomprises a first olefinic monomer unit having the structure of formula(II)

and a second olefinic monomer unit having the structure of formula (III)

wherein: m, n, and q are independently zero or 1; L¹ is selected fromC₁-C₁₂ alkylene, substituted C₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene,substituted C₁-C₁₂ heteroalkylene, and further wherein when L¹ isoptionally substituted and/or heteroatom-containing C₁-C₁₂ alkylene, L¹may be linear, branched, or cyclic; X is selected from C₃-C₃₀ alicyclicand substituted C₃-C₃₀ alicyclic; L² is selected from C₁-C₁₂ alkylene,substituted C₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂heteroalkylene, and further wherein when L² is optionally substitutedand/or heteroatom-containing C₃-C₁₂ alkylene, L² may be linear,branched, or cyclic; and R¹ is selected from acetal-containing andketal-containing substituents; L³ is selected from C₁-C₁₂ alkylene,substituted C₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂heteroalkylene, C₃-C₁₅ alicyclic, C₃-C₁₅ fluoroalicyclic andcombinations thereof; R¹¹ is selected from hydrogen, C₁-C₂₄ alkyl, andsubstituted C₁-C₂₄ alkyl; R¹² is C₁-C₂₄ alkyl or fluorinated C₁-C₂₄alkyl, with the proviso that at least one of R¹¹ and R¹² is fluorinated;and further wherein R¹¹ and R¹² can be taken together to form a ring;R¹³ and R^(13A) are independently selected from hydrogen, fluorine,C₁-C₂₄ alkyl, substituted C₁-C₂₄ alkyl, C₁-C₂₄ alkoxy, and substitutedC₁-C₂₄ alkoxy; R¹⁴ and R^(14A) are independently selected from hydrogen,fluorine, C₁-C₂₄ alkyl and substituted C₁-C₂₄ alkyl; and R¹⁵ and R^(15A)are independently selected from hydrogen, fluorine, C₁-C₂₄ alkyl, andsubstituted C₁-C₂₄ alkyl, and further wherein any two of R¹³, R¹⁴, andR¹⁵ may be taken together to form a ring and any two of R^(13A),R^(14A), and R^(15A) may be taken together to form a ring.
 25. Theprocess of claim 20, wherein the polymer comprises a first olefinicmonomer unit having the structure of formula (II)

and a second olefinic monomer unit having the structure of formula (IV)

wherein: m, n, and q are independently zero or 1; L¹ is selected fromC₁-C₁₂ alkylene, substituted C₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene,substituted C₁-C₁₂ heteroalkylene, and further wherein when L¹ isoptionally substituted and/or heteroatom-containing C₁-C₁₂ alkylene, L¹may be linear, branched, or cyclic; X is selected from C₃-C₃₀ alicyclicand substituted C₃-C₃₀ alicyclic; L² is selected from C₁-C₁₂ alkylene,substituted C₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂heteroalkylene, and further wherein when L² is optionally substitutedand/or heteroatom-containing C₃-C₁₂ alkylene, L² may be linear,branched, or cyclic; and R¹ is selected from acetal-containing andketal-containing substituents; L³ is selected from C₁-C₁₂ alkylene,substituted C₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂heteroalkylene, C₃-C₁₅ alicyclic, C₃-C₁₅ fluoroalicyclic, C₅-C₁₄arylene, substituted C₅-C₁₄, C₅-C₁₄ heteroarylene, substituted C₅-C₁₄heteroarylene, and combinations thereof; R¹³ and R^(13A) areindependently selected from hydrogen, fluorine, C₁-C₂₄ alkyl,substituted C₁-C₂₄ alkyl, C₁-C₂₄ alkoxy, and substituted C₁-C₂₄ alkoxy;R¹⁴ and R^(14A) are independently selected from hydrogen, fluorine,C₁-C₂₄ alkyl and substituted C₁-C₂₄ alkyl; R¹⁵ and R^(15A) areindependently selected from hydrogen, fluorine, C₁-C₂₄ alkyl, andsubstituted C₁-C₂₄ alkyl, and further wherein any two of R¹³, R¹⁴, andR¹⁵ may be independently taken together to form a ring and any two ofR^(13A), R^(14A), and R^(15A) may be taken together to form a ring; andR¹⁶ is selected from C₁-C₂₄ alkyl and substituted C₁-C₂₄ alkyl, C₁-C₂₄fluoroalkyl and substituted C₁-C₂₄ fluoroalkyl.
 26. The process of claim20, wherein the monomer mixture further comprises at least oneadditional olefinic monomer.
 27. The process of claim 26, wherein the atleast one additional olefinic monomer is selected from (i) a monomercontaining an acid-cleavable substituent R^(CL*); (ii) a monomercontaining an acid-inert, polar substituent, R^(P); (iii) a monomercontaining an acid-inert, nonpolar substituent, R^(NP); and (iv)combinations thereof.
 28. The process of claim 27, wherein R^(CL*) hasthe structure-(L^(1*))_(m*)-(X*)_(n*)-[(L^(2*))_(q*)-R^(1*)]_(r*)  (V) in which: m*,n*, and q* are independently zero or 1; r* is an integer of at least 1;L¹ is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂ alkylene, C₁-C₁₂heteroalkylene, substituted C₁-C₁₂ heteroalkylene, and further whereinwhen L^(1*) is optionally substituted and/or heteroatom-containingC₁-C₁₂ alkylene, L^(1*) may be linear, branched, or cyclic; X* isselected from C₃-C₃₀ alicyclic and substituted C₃-C₃₀ alicyclic; L^(2*)is selected from C₁-C₁₂ alkylene, substituted C₁-C₁₂ alkylene, C₁-C₁₂heteroalkylene, substituted C₁-C₁₂ heteroalkylene, and further whereinwhen L^(2*) is optionally substituted and/or heteroatom-containingC₃-C₁₂ alkylene, L may be linear, branched, or cyclic; and R^(1*) isselected from acid-cleavable ester, oligomeric ester, ether, carbonate,and orthoester substituents.
 29. The process of claim 27, wherein R^(P)has the structure-(L³)_(m1)-(Y)_(n1)-(L⁴)_(q1)-R¹⁸  (VI) in which: m1, n1, and q1 areindependently zero or 1; L³ is selected from C₁-C₁₂ alkylene,substituted C₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂heteroalkylene, and further wherein when L³ is optionally substitutedand/or heteroatom-containing C₁-C₁₂ alkylene, L¹ may be linear,branched, or cyclic; Y is selected from C₃-C₃₀ alicyclic and substitutedC₃-C₃₀ alicyclic; L⁴ is selected from C₁-C₁₂ alkylene, substitutedC₁-C₁₂ alkylene, C₁-C₁₂ heteroalkylene, substituted C₁-C₁₂heteroalkylene, and further wherein when L⁴ is optionally substitutedand/or heteroatom-containing C₃-C₁₂ alkylene, L⁴ may be linear,branched, or cyclic; and R¹⁸ is an acid-inert polar organic groupcontaining a heteroatom with a Pauling electronegativity greater thanabout 3.00.
 30. The process of claim 27, wherein R^(P) is selected fromlactone, anhydride, sulfonamide, fluoroalkanol, alkanol, alicyclicalkanol, esters, ethers, and a combination thereof.
 31. The process ofclaim 27, wherein R^(NP) is C₁-C₁₈ hydrocarbyl or fluorinated C₁-C₁₈hydrocarbyl.
 32. The process of claim 24, wherein the first olefinicmonomer unit is derived from a monomer having a structure selected fromthe formulae


33. The process of claim 32, wherein R¹⁵ is selected from hydrogen,fluorine, C₁-C₂₄ alkyl, and fluorinated C₁-C₂₄ alkyl.
 34. The process ofclaim 25, wherein the first olefinic monomer unit is derived from amonomer having a structure selected from the formulae


35. The process of claim 34, wherein R¹⁵ is selected from hydrogen,fluorine, C₁-C₂₄ alkyl, and fluorinated C₁-C₂₄ alkyl.